Liquid containers such as bottles or beverage cans are produced in that preforms are stretch-blown in blow molds in a stretch-blowing installation. The preforms as well as the liquid containers made thereof are normally inspected and defective items are segregated, for example, in that the defective items are detected, evaluated and ejected from a series of such preforms or liquid containers running on a conveyor belt.
German patent DE 102 59 589 B3 discloses a method for producing hollow objects made of plastic in that heated preforms are stretch-blown, whereby the preforms are inspected prior to being heated and defective preforms are ejected. In this context, at least some of the defective preforms are heated and are only ejected after being heated, preferably by a sorting station that can be controlled by an inspection station and by an evaluation unit of the inspection station.
German utility model DE 201 14 032 U1 discloses a device for segregating defective preforms. This device includes a controllable sorting member that acts directly on the preforms. The sorting member pushes the preform essentially in the axial direction, thus forcing the neck collar of an individual preform against a bearing surface for the preform. An evaluation unit controls a stationary pneumatic cylinder with a piston rod. If the sorting member receives a segregating signal from the evaluation unit, the pneumatic cylinder moves a tappet pulse-like downwards from its idle position into its ejecting position and then back to its idle position. In this process, the tappet strikes the head of the preform in question, presses it downwards and thus segregates it.
German patent DE 195 16 403 C2 discloses a device with which bottles being transported on a first conveyor belt are selectively transferred to a second conveyor belt. The device includes a tappet that is mounted so as to move back and forth along a straight trajectory, said tappet being driven by a drive into the path of motion of the bottles, thus imparting a given bottle with a motion pulse oriented perpendicular to the conveying direction. When the tappet is driven into the path of motion of the objects, it has a motion component that is directed downwards. Preferably, the tappet is fastened to the piston rod of a pneumatic cylinder that points obliquely downwards and it is installed so as to move between two vertical parallel plates between which the pneumatic cylinder is likewise attached.
German patent DE 27 04 614 discloses a device for distributing upright bottles, comprising a first transporter star and a second transporter star as well as an inlet channel and an outlet channel. Movable pistons are present for pushing the bottles either into the outlet channel of the first transporter star or into an outlet channel of the second transporter star, depending on the piston that has been actuated.
German patent application DE 36 31 879 discloses a device for segregating defective bottles. A deflecting mechanism in the form of a helical spiral, which is actuated by a detection station for defective bottles, imparts the bottles with a motion pulse perpendicular to the running direction of the conveyor. The deflecting mechanism has a motor-driven shaft having a brush segment whose contour lies on a helical spiral ascending in the running direction of the conveyor.
German patent DE 32 04 114 C2 discloses a device for sorting bottles that are standing upright. On one side of a horizontal conveying surface, there is a controllable deflector, for instance, a pneumatically actuated tappet, that diverts certain bottles from a first conveyor belt onto a second conveyor belt situated parallel thereto. A guide surface located on the other side of the conveying surface has a collecting zone that is slanted with respect to the vertical and positioned to the side next to the conveying surface, whereby said collecting zone, together with a support element that engages with the bottom of the bottle, serves to hold in a stable slanted position any bottles that tip over the edge of the conveying surface. In the collecting zone, there is at least one transportation member that runs in the direction of the second conveyor belt and that engages with the slanted bottles.
European patent EP 1 079 120 B1 discloses a compressed-air maintenance unit and German patent DE 102 47 869 B4 discloses a ram cylinder actuated by a pressurized medium and these publications illustrate the basic technologies for segregating elements as cylinder valve units in devices for segregating defective preforms or bottles.
U.S. Pat. No. 3,745,890 describes ram without ram rings. The collaboration between similar materials (ram-cylinder) is known but U.S. Pat. No. 3,745,890 does not disclose that articles should be sorted out and how a ram for sorting out should be arranged.
The German Utility Patent DE 94 07 563 relates to a device for selectively transferring objects transported on a conveyor, especially bottles, to a second conveyor. The downward directed movement component of a ram exercises via friction on a point of impact of the bottle or the like, a downward force, which counteracts with the tilt momentum caused by the horizontal movement component of the ram on the bottle. Further, the impact is mitigated by the downward directed movement component.
When it comes to modern installations for segregating articles, for instance, defective preforms or liquid containers such as bottles or beverage cans, stricter requirements are made of the cycle rate in relation to the throughput or to the segregation of the articles in such an installation. The articles should be quickly transported, processed and segregated in the installation. The segregation is done, for instance, by means of the above-mentioned segregating elements, namely, the cylinders, the cylinder housing, the valves and the pistons installed in the cylinders. The piston sealing elements are configured according to the state of the art so as create a soft sealing. Soft-sealing materials have relatively high coefficients of friction, which detrimentally places an upper limit on the cycle rate. Moreover, soft-sealing materials quickly turn brittle, tear and become permeable for the medium that flows via the valves or from the cylinder. Besides, an uneven, roughened piston sealing element that displays elevations and projections or the like slides more slowly over the sliding surface of the cylinder housing than an undamaged piston sealing element does. The service life of the damaged piston sealing element and thus the service life of the piston are reduced. Another drawback of soft-sealing materials exists for the sealing elements in the area of the piston since lubricants such as, for example, oils, are employed in order to prevent the soft-sealing materials from becoming roughened, and these oils become gummy due to the fast motion of the piston, in turn, impairing the sliding properties. All in all, the functionality of the sorting procedure of the articles and the cycle rate pertaining to the motions of the piston and thus the entire installation are detrimentally affected.